The major objective of this project is to evaluate the therapeutic effects of defibrination with Ancrod (Arvin) in human rapidly progressive glomerulonephritis. The rationale for this proposal is based on the clear-cut demonstration of the beneficial effects of Ancrod in experimental glomerulonephritis. The effect of Ancrod on glomerular fibrin deposition, epithelial crescents, and renal function will be studied. These studies are intended to improve our understanding of the role of coagulation in the glomeruli in destructive glomerular disease, and to learn more of the interactions of pathogenetic mechanisms mediated by immunologic events and by coagulation. Studies will be done in limited numbers of patients ih whom fibrin and crescents are found in the renal biopsies. The coagulation and fibrinolytic mechanisms will be studied in detail (including specific assay for fibrinopeptide A) prior to, during, and following the administration of Ancrod.